Range hood ducting shall be constructed of single wall material, galvanized steel, stainless steel or copper. Corrugated flex ducting not allowed as they would trap grease and could start a fire.
Single wall ducts serving range hood require a minimum of 1” clearance to combustible materials since 1997.
Range hood ducting shall be secured with (3) small sheet metal screws at each joint connection, with duct tape or aluminum tape over connections.
Vertical clearance from cook top to hood shall be 30” inches with exception of 24” inches cook top to microwave.
Hood must be the same size as cook top, 30” cook top, 30” hood. 36”
Cook top 36” hood.
Range hoods shall discharge to exterior of the building through single wall ducting. The duct serving the hood shall have a smooth interior surface, and be air tight. The hood or vent piping shall be equipped with a back draft damper.
Hoods or microwave ovens with rectangular discharge openings must have proper transition connection and be sealed properly.
Ducts serving range hoods shall not terminate in attic, crawl spaces or inside the building.